Yu Hang Lai

Laser induced periodic surface structure formation in germanium by strong field mid IR laser solid interaction at oblique incidence.

Laser induced periodic surface structures (LIPSS or ripples) were generated on single crystal germanium after irradiation with multiple 3 µm femtosecond laser pulses at a 45° angle of incidence. High and low spatial frequency LIPSS (HSFL and LSFL, respectively) were observed for both s- and p-polarized light. The measured LSFL period for p-polarized light was consistent with the currently established LIPSS origination model of coupling between surface plasmon polaritons (SPP) and the incident laser pulses. A vector model of SPP coupling is introduced to explain the formation of s-polarized LSFL away from the center of the damage spot. Additionally, a new method is proposed to determine the SPP propagation length from the decay in ripple depth. This is used along with the measured LSFL period to estimate the average electron density and Drude collision time of the laser-excited surface. Finally, full-wave electromagnetic simulations are used to corroborate these results while simultaneously offering insight into the nature of LSFL formation.

High spatial frequency laser induced periodic surface structure formation in germanium by mid-IR femtosecond pulses

Formation of high spatial frequency laser induced periodic surface structures (HSFL) in germanium by femtosecond mid-IR pulses with wavelengths between

The roles of photo-carrier doping and driving wavelength in high harmonic generation from a semiconductor

\lambda=2.0

Experimental investigation of strong-field-ionization theories for laser fields from visible to midinfrared frequencies

and

Universal pulse dependence of the low-energy structure in strong-field ionization

3.6 \; \mathrm{\mu m}

Femtosecond laser damage of germanium from near- to mid-infrared wavelengths

was studied with varying angle of incidence and polarization. The period of these structures varied from

Tunable mid-infrared source of light carrying orbital angular momentum in the femtosecond regime

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High-order harmonic generations in intense MIR fields by cascade three-wave mixing in a fractal-poled LiNbO_3 photonic crystal

to

Ionization and fragmentation of methane with intense mid-infrared fields

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Ionization of alkaline earth atoms in intense femtosecond laser fields

. A modified surface-scattering model including Drude excitation and the optical Kerr effect explains spatial period scaling of HSFL across the mid-IR wavelengths. Transmission electron microscopy (TEM) shows the presence of a